Crazy About Worms
On 7 May, while walking around Peaks at about 6:20 p.m., I noticed a large number of gulls congregated offshore in Hussey Sound, north of Whaleback. Through binoculars, I saw that it was a larger group than I had first thought, spread northwestward past Spar Cove, about 250 birds in all. The mixed group of Herring Gulls, Great Black-backed Gulls, Common Eiders, and Double-crested Cormorants were creating quite a commotion. Herring Gulls (by far the most abundant species) were yelling and dive-bombing other birds, stealing food from eiders and cormorants and each other. Eiders and cormorants were diving enthusiastically, apparently for something abundant. I strained to see what they were fighting over. My best guess: some sort of worms. Gulls would hover briefly before diving into the water, emerging with a worm-like prize (sometimes about 8-12 inches long), only to be chased by other gulls trying to steal it.
From my previous life teaching marine biology and researching marine worms, I knew that many marine worms spawn synchronously, sometimes using environmental cues. The details depend on the species of worm, but unfortunately I was not able to identify the species at a distance through binoculars.
Patty and Kathy observed large numbers of sandworms yesterday (8 May) at ferry beach. Let’s assume, for illustration purposes, that the worms in Hussey Sound were that same species (Alitta virens). According to Wilson and Ruff 1988, this species is harvested for bait (a multi-million dollar industry), lives for 4-5 years, and reaches lengths of up to 900 mm. Spawning occurs in April-May when water temperature exceeds 7-8 degrees C and is timed to the phase of the moon. Males undergo metamorphosis, into a form that is adapted for swimming, and release their sperm into the water. Females take the sperm into their burrows in the sand, where fertilization occurs. Both sexes die after spawning, much like Pacific salmon. The spent bodies of the worms, washed seaward in the tides, may present opportunistic feeders like hungry gulls, eiders and cormorants with a bonanza.
As already noted, we do not know whether the worms that we observed were, in fact, sandworms. In another abundant species called blood worms (Glycera dibranchiata, described in the same report), both sexes transform into swimming forms, release gametes into the water, and die. If the subject of birds eating marine worms is not your cup of tea, then perhaps you would be interested in spawning marine worms that are eaten as a delicacy by humans, such as palolo worms.
By Sam Wainright
Reviewed by Michelle Brown, Marty, Michael LaCombe, Patty Wainright